Antimicrobial and antioxidant activities of the fruits of bemavo, a variety of Ravenala madagascariensis Sonn. (Strelitziaceae)

This work was designed to evaluate the antibacterial and antioxidant activities of the fruit extracts from bemavo, a variety of Ravenala madagascariensis. Methanolic extracts from pericarp (PME), seed (SME) and aril (AME) were tested against 5 Gram positive and 6 Gram negative of pathogenic bacteria using disk diffusion and microdilution methods. At 1000 µg/ml, all extracts prevented selectively the growth of at least 5 of the tested bacteria with Inhibition Zone Diameter (IZD) ranking from 8.5 mm to 19 mm. The best activity was recorded with PME which was active against 81.8 % of the studied bacteria with 63.6 % of IZD higher than 14 mm: 15 mm on Yersinia enterocolitica, Salmonella enterica, Shigella flexneri, and Listeria monocytogenes, 16 mm on Staphylococcus aureus, 18 mm on Enteroacter aerogenes, and 19 mm on Vibrio fischeri. Clostridium perfringens and Bacillus cereus were resistant to the three extracts. The great majority (97 %) of MCI recorded were ≤1000 µg/ml, 84.8 % were ≤500 µg/ml, 12.1 % between 500 µg/ml and 1000 µg/ml. Enterobacter aerogenes was the most sensitive to the three extracts. The three extracts were bactericidal against Enterobacter aerogenes and Clostridium perfringens, bacteriostatic against Salmonella enterica and Bacillus cereus and bactericidal or bacteriostatic against the remaining strains. The antioxidant activity of extracts was determined by the method using free radical scavenging against DPPH. Compared with ascorbic acid (IC₅₀=7.320 µg/ml), SME (IC₅₀=0.568 µg/ml) and AME (IC₅₀=3.792 µg/ml) were 12.9 and 6.5 times more active respectively. Phenolic compounds present in three extracts could be responsible for antimicrobial and antioxidant activities of the bemavo fruit methanol extracts.